Plants are the foundation for life on the planet and botanic gardens serve an important purpose in conserving plant diversity and preventing species extinction. Widely distributed worldwide, these gardens habour thousands of species, but combined knowledge of their content and coverage is unclear.

In an analysis of world's botanic gardens, UK researchers identified 3,269 collections in 180 countries with known holdings of more than 105,000 plant species combined–corresponding to about 30 per cent of accepted species in The Plant List covering 93 per cent of all vascular plant families.

Based on GBIF-mediated occurrences, the author determined the laditudinal ranges of held species and found a remarkable bias towards temperate species, counter to the natural gradient where the most diversity is found in the tropics. Mapping combined collections against a phylogenetic tree of all accepted land plant genera revealed another striking bias as non-vascular lineages are almost completely undocumented.

These findings combined suggest a remarkable degree of worldwide coverage, but also points to gaps to be addressed for conservation in botanic garden collections.